I just bought a 97 chevy z71 with a 5.7. I was wondering can I do anything to get better gas milage?

 

Add E-fans and hotter ignition system like MSD.

 

tuneup with all ac delco parts
change all fluids to synthetic
find a station that sells non ethanol fuel

clean out the tool box or get rid of any extra weight in the bed
might try a k&n air filter

start slow and never drive over speed limit.

check you differential ratio, if it 3.73 you might change to 3.42 but your power will suffer.
but you are looking for increased mpg, not power.

remember these trucks are like bricks going down the road,
high mileage was not one of there selling points.

my son has one of the new 1500 4x4 cc with the energy management systems.
truck has lots of power but gets great mpg, as it runs on 4 cylinders when not under strain.
new technology, but they cost big bucks.

 

My set up in my 99 Tahoe gets 21 MPG's highway and bout 18 all around average.

 

I put an electric fan on my 97 suburban and it gets about 18mpg average at 228000 miles the clutch fan is a big drag on fuel economy I bought 2 16" electrics from Oriellys one is wired to the key and the other is an "aux" fan for the summer time( gets hot here in Missouri).
There are several ways to wire them up. I would explore all possibilities before doing it.